Internal combustion engine



Oct.- 29, 1935.

W. ENDRES INTERNAL COMBUSTION ENGINE- Original Filed July 24, 1.930

Patented @et. 29, 1335 UNITED I STATES INTERNAL COMBUSTION ENGINEporation of Germany Original application July 24, 1930, Serial no.

470,291. Divided and this application September 10, 1934, Serial No.743,390. In Germany July 29, 1929 2 Claims. (01. 123-119) This inventionrelates to internal combustion engines of the type operating with airscavenging, and more particularly to engines of this character adaptedfor use in aircraft.

. One object of the invention is the provision of an aircraft engine,operating with air scavenging, the supply of scavenging air to theengine being substantially constant at various elevaions.

Other objects and advantages of the invention will be apparent from thefollowing description, the appended claims, and the accompanyingdrawing, in which- Fig. 1 is a diagrammatic view of an aircraft engineembodying the present invention, the scavenging air blower for theengine having a variable speed drive; and

Fig. 2' is a view of a modified form of the invention, in which anauxiliary blower is adapted to supply air to the main scavenging airblower.

This application is a division of application Serial No. 470,291, filedJuly 24, 1930.

Internal combustion engines of the customary construction, having airscavenging, do not operate at full efliciency when thesurrounding air isat less than atmospheric pressure, since the amount of air charged inthe cylinders is decreased under such conditions. When aircraft arepowered by engines-operating with scavenging air, in accordance withthis invention, means are provided for maintaining the scavenging airflow from a scavenging air pump at a substantially definite pressure sothat the aircraft engine may operate efficiently when at highelevations.

Referring to the accompanying drawing, in which preferred embodiments ofthe invention are illustrated, and first with reference to Fig.

1, ll designates an internal combustion engine forming the power unit ofan aircraft. Preferably the engine is of the two cycle double actingDiesel type. It is shown connected to the propeller shaft I 5. Connectedto the engine cylinder or cylinders is a scavenging pipe I2 throughwhich scavenging air is supplied so as to scavenge burnt gases and tocharge the cylinder with a supply of free air into which the fuel may beintroduced. The exhaust gases flow out through the exhaust pipe l3.

A supply of scavenging air is created by the scavenging air blower l4,which may be of the turbine type, or of the positive displacement type.This blower receives air from the exterior and supplies it to thescavenging air ports of the engine cylinder, at some definitepredetermined pressure. The blower is connected by suitable gearing, asshown, to the main shaft i5, and is adapted to operate, underordinaryconditions, at

a speed considerably in excess of the engine gine cylinder with freshair. 1

When operating at the ground level, or at small distances from theground, the aircraft engine operates at a high efliciency as it receivesthe full charge of air intended, the size and the speed of the blower l4being so coordinated with the scavenging air requirements as to produceefficient operation of the engine. 'When the aircraft is at highelevations, however, if the speed of the blower was constant, it wouldfail to supply suflicient air to the engine cylinder and a 25 loss ofefficiency and a decrease in power would result. By means of thevariable transmission gearing l6, however, the speed ratio of the blowerIt may be increased so that the scavenging air supplied to the cylinderis at the proper predetermined pressure, substantially the same as thepressure required at ground levels or under the ordinary atmosphericpressure conditions.

The arrangement as shown in Fig. 1 is especially adapted for use on thesmaller powered engines, for with smaller powered engines the gearsystem by which the blower. is driven would not be unduly large andheavy. Where the engine is of large size, and the power required fordrivingthe blower is very substantial, an arrangement such as is shownin Fig. 2 may be employed. Here the engine 2 l, preferably of the twocycle Diesel type, has its scavenging air pipe 22 connected to the mainscavenging air' blower 24, the exhaust the outlet side of the auxiliaryblower 26 to the' suction side of the blower 24, and this pipe is provided with an inlet checkvalve 29 through which air may be drawn fromthe exterior, the valve 29 being adapted to close automatically when thepressure within the pipe 28 exceeds the outside pressure. At the groundlevel, and at low flying elevations, the drive 21 is maintained inneutral so that the blower 26 is'inoperative, air being drawn to thescavenging air blower '24 through the check valve 29 or through theblower 26 if the latter is of the turbine type. v

The size of the blower 24, and its speed of operation are such that thedesired pressure of the scavenging air flow to the engine is obtainedfor satisfactory and economical operation under normal air pressureconditions or at ground level, and with the auxiliary blower 26 idle.When operating at higher altitudes, the blower 26 may be operated at asuitable speed so that air is drawn from the exterior and supplied bythis auxiliary blower at substantially normal atmospheric pressure, thisair being then drawn in by main blower ii to be supplied at the properpredetermined pressure to the engine cylinder or cylinders. As the powerrequired for driving the auxiliary blower is comparatively small ascompared with the power required for driving the main blower 24, the

selective speed transmission 21 may be quite small and compact. It willbe apparent that as long as the auxiliary blower supplies air to themain blower 24 at normal atmospheric pressure, or at about 14.7 poundsper square inch, theproper predetermined pressure of the scavenging airshaft of the blower 24 may be sufficient to provide a satisfactorysupply of scavenging air to the engine cylinder at the higher altitudes.

The embodiments of the invention shown in Figs. 1 and 2 are preferablyprovided with devices such as a control throttle in the exhaust line ofthe engine to provide for maximum loading or charging of air in thecylinder after the ordinary scavenging cycle ceases. In this way thepressure of the air charge in the cylinder may reach the desired degreeat the beginning of the compression stroke. Such throttles are not shownas their details form no part of the present invention.

While the forms of apparatus herein described constitute preferredembodiments of the invention, it is to be understood that the inventionis not limited to these precise forms of apparatus,

and that changes m y be made therein without departing from the scope ofthe invention which is defined in the appended claims.

What is claimed is:

1. In a power system for aircraft, an internal combustion engineoperating with air scavenging, a scavenging air blower operatlvelyconnected to the engine shaft to provide a scavenging air flow to theengine at a definite pressure when operating under normal atmosphericpressure conditions, and a variable speed blower for supplying air tosaid scavenging air blower at substantially normal atmospheric pressure,and a variable speed transmission between said blowers.

2. In a power system for aircraft, an internal combustion engineoperating with air scavenging, a scavenging air blower providing ascavenging air flow to the engine at a definite pressure when operatingunder normal atmospheric pressure conditions, a variable speed blowerdriven by said scavenging air blower for supplying air to saidscavenging air blower at substantially normal atmospheric pressureregardless of the elevation of the aircraft, and a variable speed trans-WILHELM amass:

